perldoc > XML::DOM

📛 NAME

XML::DOM - A perl module for building DOM Level 1 compliant document structures

🚀 Quick Reference

Use CaseCommandDescription
🔍 Parse XML filemy $parser = new XML::DOM::Parser; my $doc = $parser->parsefile("file.xml");Parse an XML file and return a DOM document object
🔎 Find elements by tagmy $nodes = $doc->getElementsByTagName("CODEBASE");Get a NodeList of all elements with a given tag name
🖨️ Print to file$doc->printToFile("out.xml");Write the DOM document to an XML file
📄 Print to stringprint $doc->toString;Convert the DOM document to a string
🧹 Clean up memory$doc->dispose;Break circular references to avoid memory leaks

💻 SYNOPSIS

 use XML::DOM;

 my $parser = new XML::DOM::Parser;
 my $doc = $parser->parsefile ("file.xml");

 # print all HREF attributes of all CODEBASE elements
 my $nodes = $doc->getElementsByTagName ("CODEBASE");
 my $n = $nodes->getLength;

 for (my $i = 0; $i < $n; $i++)
 {
     my $node = $nodes->item ($i);
     my $href = $node->getAttributeNode ("HREF");
     print $href->getValue . "\n";
 }

 # Print doc file
 $doc->printToFile ("out.xml");

 # Print to string
 print $doc->toString;

 # Avoid memory leaks - cleanup circular references for garbage collection
 $doc->dispose;

📖 DESCRIPTION

This module extends the XML::Parser module by Clark Cooper. The XML::Parser module is built on top of XML::Parser::Expat, which is a lower level interface to James Clark's expat library.

XML::DOM::Parser is derived from XML::Parser. It parses XML strings or files and builds a data structure that conforms to the API of the Document Object Model as described at http://www.w3.org/TR/REC-DOM-Level-1. See the XML::Parser manpage for other available features of the XML::DOM::Parser class. Note that the 'Style' property should not be used (it is set internally.)

The XML::Parser *NoExpand* option is more or less supported, in that it will generate EntityReference objects whenever an entity reference is encountered in character data. I'm not sure how useful this is. Any comments are welcome.

As described in the synopsis, when you create an XML::DOM::Parser object, the parse and parsefile methods create an *XML::DOM::Document* object from the specified input. This Document object can then be examined, modified and written back out to a file or converted to a string.

When using XML::DOM with XML::Parser version 2.19 and up, setting the XML::DOM::Parser option *KeepCDATA* to 1 will store CDATASections in CDATASection nodes, instead of converting them to Text nodes. Subsequent CDATASection nodes will be merged into one. Let me know if this is a problem.

When using XML::Parser 2.27 and above, you can suppress expansion of parameter entity references (e.g. %pent;) in the DTD, by setting *ParseParamEnt* to 1 and *ExpandParamEnt* to 0. See Hidden Nodes for details.

A Document has a tree structure consisting of *Node* objects. A Node may contain other nodes, depending on its type. A Document may have Element, Text, Comment, and CDATASection nodes. Element nodes may have Attr, Element, Text, Comment, and CDATASection nodes. The other nodes may not have any child nodes.

This module adds several node types that are not part of the DOM spec (yet.) These are: ElementDecl (for <!ELEMENT ...> declarations), AttlistDecl (for <!ATTLIST ...> declarations), XMLDecl (for <?xml ...?> declarations) and AttDef (for attribute definitions in an AttlistDecl.)

📦 XML::DOM Classes

The XML::DOM module stores XML documents in a tree structure with a root node of type XML::DOM::Document. Different nodes in tree represent different parts of the XML file. The DOM Level 1 Specification defines the following node types:

In addition, the XML::DOM module contains the following nodes that are not part of the DOM Level 1 Specification:

Other classes that are part of the DOM Level 1 Spec:

Other classes that are not part of the DOM Level 1 Spec:

📦 XML::DOM package

📊 Constant definitions

The following predefined constants indicate which type of node it is.

Usage:

  if ($node->getNodeType == ELEMENT_NODE)
  {
      print "It's an Element";
  }

Not In DOM Spec: The DOM Spec does not mention UNKNOWN_NODE and, quite frankly, you should never encounter it. The last 4 node types were added to support the 4 added node classes.

🌐 Global Variables

$VERSION The variable $XML::DOM::VERSION contains the version number of this implementation, e.g. "1.43".

🛠️ METHODS

These methods are not part of the DOM Level 1 Specification.

getIgnoreReadOnly and ignoreReadOnly (readOnly) The DOM Level 1 Spec does not allow you to edit certain sections of the document, e.g. the DocumentType, so by default this implementation throws DOMExceptions (i.e. NO_MODIFICATION_ALLOWED_ERR) when you try to edit a readonly node. These readonly checks can be disabled by (temporarily) setting the global IgnoreReadOnly flag. The ignoreReadOnly method sets the global IgnoreReadOnly flag and returns its previous value. The getIgnoreReadOnly method simply returns its current value. 
 my $oldIgnore = XML::DOM::ignoreReadOnly (1);
 eval {
 ... do whatever you want, catching any other exceptions ...
 };
 XML::DOM::ignoreReadOnly ($oldIgnore);     # restore previous value
Another way to do it, using a local variable: 
 { # start new scope
    local $XML::DOM::IgnoreReadOnly = 1;
    ... do whatever you want, don't worry about exceptions ...
 } # end of scope ($IgnoreReadOnly is set back to its previous value)
isValidName (name) Whether the specified name is a valid "Name" as specified in the XML spec. Characters with Unicode values > 127 are now also supported. getAllowReservedNames and allowReservedNames (boolean) The first method returns whether reserved names are allowed. The second takes a boolean argument and sets whether reserved names are allowed. The initial value is 1 (i.e. allow reserved names). The XML spec states that "Names" starting with (X|x)(M|m)(L|l) are reserved for future use. (Amusingly enough, the XML version of the XML spec (REC-xml-19980210.xml) breaks that very rule by defining an ENTITY with the name 'xmlpio'.) A "Name" in this context means the Name token as found in the BNF rules in the XML spec. XML::DOM only checks for errors when you modify the DOM tree, not when the DOM tree is built by the XML::DOM::Parser. setTagCompression (funcref) There are 3 possible styles for printing empty Element tags: Style 0: <empty/> or <empty attr="val"/> (default) Style 1: <empty></empty> or <empty attr="val"></empty> Style 2: <empty /> or <empty attr="val" /> (useful for XHTML, see Appendix C) You can control which style is used for a particular Element by calling XML::DOM::setTagCompression with a reference to a function that takes 2 arguments (tag name and Element). The function should return 0, 1 or 2. E.g. 
 XML::DOM::setTagCompression (\&my_tag_compression);

 sub my_tag_compression
 {
    my ($tag, $elem) = @_;

    # Print empty br, hr and img tags like this: <br />
    return 2 if $tag =~ /^(br|hr|img)$/;

    # Print other empty tags like this: <empty></empty>
    return 1;
 }

🏗️ IMPLEMENTATION DETAILS

👀 SEE ALSO

⚠️ CAVEATS

The method getElementsByTagName() does not return a "live" NodeList. Whether this is an actual caveat is debatable, but a few people on the www-dom mailing list seemed to think so. I haven't decided yet. It's a pain to implement, it slows things down and the benefits seem marginal. Let me know what you think.

✍️ AUTHOR

Enno Derksen is the original author.

Send patches to T.J. Mather at <tjmather AT maxmind.com>.

Paid support is available from directly from the maintainers of this package. Please see http://www.maxmind.com/app/opensourceservices for more details.

Thanks to Clark Cooper for his help with the initial version.

XML::DOM □✕
📛 NAME 🚀 Quick Reference 💻 SYNOPSIS 📖 DESCRIPTION
📦 XML::DOM Classes 📦 XML::DOM package
🏗️ IMPLEMENTATION DETAILS 👀 SEE ALSO ⚠️ CAVEATS ✍️ AUTHOR

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